The difference is that existing programs require the user to correct each word individually from a drop-down list of alternatives, or else to retype or reutter the words.
We were using typewriters, where the state of the art way to correct a typo was to backspace and put a strip of white paper behind the key and retype the word.
Those students will then retype that passage at the start of each online session, with Coursera able to check typing speeds and rhythms to ensure that the same registered student is at the keyboard each time.